Related Materials And Properties Of CdS/CdTe Thin Film Solar Cells

CdS/CdTe thin film solar cells is a novel kind of thin film batteries, which has abroad development prospects in photovoltaic industry. CdS has relatively stablechemical properties and is II-VI compound semiconductor. The band gap of thesemiconductor material is2.42eV and the vast majority of the sunlight can through it.CdS thin film is used as a good n-type window material for CdS/CdTe thin film solarcells. CdTe is a direct band gap semiconductor material. Its band gap is1.46eV. And itis a good photovoltaic materials capable of forming a good CdS heterojunction. It canbe formed with CdS to be good heterojunction. Therefore, the quality of CdS andCdTe thin film will directly affect the final performance and battery life of the solarcell.This paper mainly has three aspects:1、 CdS thin film is prepared by chemical bathdeposition. A systematic research was on CdS crystalline structure by changing theexperimental conditions, such as deposition temperature, deposition time, pH of thereaction solution and annealing conditions. X-ray diffraction, scanning electronmicroscopy and UV-visible absorption spectroscopy tests were analyzed in terms ofits structure, morphology, optical properties. By discussion the optimum conditionsare concluded. Conclusions are as follows:(1) when the deposition time was60min, the deposition of CdS thin films are ofuniform density and thickness is stable.(2) When the deposition temperature is80℃，it is very conducive to thehexagonal surface growth of CdS and forms a dense film relatively. In fact, with thedeposition temperature, the optical absorption edge shifts to red wavelength, as aresult, gap band of CdS is narrowed.(3) As the pH of the solution increases, the morphology of the CdS film has beengreatly changed. When pH equals10.5, the obtained CdS has the best density andwith the pH raised, it is conducive to the hexagonal CdS surface growth.(4) Annealing treatment can narrow the band gap of CdS. Coating CdCl2methanol solution before annealing treatment may be effective in promoting growthand CdS recrystallized grains. The film becomes more compact and uniform.(5) The study found that the annealing temperature at400℃is the best. Whenannealing temperature is higher than400℃, CdS film will be oxidized. 2、The paper has also studied CdTe films prepared by electrochemical deposition.By X-ray diffraction, atomic force microscopy and UV tests, the effects of the electricpotential and annealing treatment conditions on the crystal structure, morphology andoptical properties of CdTe thin films are discussed.3、Finally a new type of solar cell structure is made of the CdS and CdTe thinfilms. A series of tests on its electrical characteristics are carried on.